The aims of this proposal are to 1) further analyze the mechanism of action of bleomycin in vitro, (2) restrict the cytotoxicity of bleomycin to tumor cells, 3) understand the basis for resistance to the growth inhibitory properties of bleomycin and 4) study the degradation of DNA by VP-16-213. In vitro experiments with bleomycin will 1) define the role of metals other than iron and of phosphate anion in the action of the drug; 2) determine the early lesions in DNA and the final products of DNA degradation; 3) reveal the origin of the oxygen present in the products of DNA degradation; and 4) search for a covalent association with DNA. Cellular studies with bloemycin will examine ways in which the specificity of the drug for tumor cells can be enhanced. Experiments will focus on the role of oxygen in drug activity and on the modification of drug uptake. Covalent conjugates of bloemycin with bovine serum albumin, IgG and monoclonal antibodies will be prepared and their cytotoxic activity determined and compared to that of free drug. Bleomycin-resistant cells will be evaluated for the stability of the resistant phenotype, cross-resistance to other drugs, alterations in drug uptake, changes in membrane components and karyotype. Several new proteins induced in the drug-resistant cells will be purified, characterized in terms of localization and biosynthesis and antibodies will be developed against them. An in vitro assay for the degradation of DNA by VP-16-213 will be developed. The effects of VP-16-213 on DNA synthesis and degradation of adenovirus and SV40 DNA in infected cells will be determined. Singe-stranded breaks in adenovirus DNA will be characterized after infection of HeLa cells.